One way to do this is by using the ChangeDetector.

I do not know of the Symmetrical Difference tool, but you probably can run that as well using a PythonCaller in FME.

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Looking at the Symmetrical Difference tool, this can be done with an AreaOnAreaOverlayer followed by a tester, overlaps = 1.

You should try the ChangeDetector, see if that works for you.

Thanx nielsgerrit and liamfez. I am going to try that. But first i am going home. End of the workingday here in the Netherlands . Have a nice evening.

That looks like the AreaOnAreaOverlayer where the result of _overlaps >1 is filtered out.

Good morning all,

The AreaOnAreaOverlayer works for me. Thanx nielsgerrits and jkr_wrk .

I was just wondering the following:
- is it also possible to indicate in this tool which areas have become smaller than the original and which areas have become larger than the original. Now I see what has changed in relation to each other, but I do not see the above. 
- I would also like to ask myself the following. Is there also a kind of topology transformer in FME to discover gaps between areas that need to connect to each other and other topology keys? ArcGISPro also has this feature, but I feel like FME can do this a bit more intuitively.

Greetings

Use the AreaCalculator… twice.

Excuse me, I didn't explain it quite right. I know the AreaCalculator and I don't need it in this example. My concern is as follows.

I want to know what has changed in the dataset 2 of the square compared to dataset 1. The yellow area in dataset 2 has become smaller relative to dataset 1 and the red area in dataset 2 has become larger relative to dataset 2. 

Excuse me, I didn't explain it quite right. I know the AreaCalculator and I don't need it in this example. My concern is as follows.

I want to know what has changed in the dataset 2 of the square compared to dataset 1. The yellow area in dataset 2 has become smaller relative to dataset 1 and the red area in dataset 2 has become larger relative to dataset 2. 

I think what @jkr_wrk was suggesting with the two AreaCalculators was that if you used 1 AreaCalculator to get the initial polygon areas, and then after using the AreaOnAreaOverlayer you used another one. You could take the difference between those two areas for any given polygon. That should tell you if a polygon got smaller or larger.